He added that whether the trio were really possessed, or had simply convinced themselves that they were, was not for doctors to comment on.

Naturally, the case can be explained in more than one way. Maybe it was a kind of group hysteria. Maybe it was a publicity stunt. Or maybe it was actual spirit possession, something that is often claimed to be a possible danger posed by Ouija boards.

Bernardo Kastrup's new book, combatively titled Why Materialism Is Baloney, makes a case for monistic idealism - the philosophical position that everything is ultimately part of consciousness, and that there is no dualistic divide between physical reality and the mind. It's a brisk, compelling read, written in a user-friendly style and making use of a series of metaphors or analogies to advance the argument.

What I'd like to do here is convey the style of the book and the gist of its message through some excerpts. I've previously quoted from Kastrup's defense of the filter/receiver theory of the brain, and I won't rehash that material in this post. But the book covers a lot of other ground. Let's look at some highlights.

Before we get unto the meat of the book, I want to cite an interesting anthropological detail about the downside of believing in an afterlife. Kastrup:

Take, for instance, the Zuruaha tribe in the Brazilian Amazon: their worldview entails the belief that the soul ('asoma') reunites with lost relatives after physical death. This belief is so deeply internalized that, in the period between 1980 and 1995, 84.4% of all deaths among adults – defined as people over 12 years old – in their society was caused by suicide. As a result, a population known for excellent health and very few diseases has an average life expectancy of only 35 years. Faced with what you and I would consider completely ordinary crises and frustrations – like disputes of ownership, control of female sexuality, periods of low self-esteem etc. – many Zuruaha simply choose to rejoin their lost loved ones in the afterlife. They don't do it for heroic status, or for religious and sociopolitical causes – like the phenomenon of martyrdom – but simply as an attempt to improve their personal situations. To you and me, it would be like choosing to move to another town.

As far as physical survival is concerned, maybe it's just as well that most of us are not quite as sure of an afterlife as the Zuruaha!

Now for the book's more philosophical content. Kastrup begins by pointing out the weaknesses of the strict materialist case. For instance, he takes aim at the notion that the activation of a few specific neurons, while unmeasurable by instruments, is enough to generate complex subjective experiences:

Materialists often take the notion of specificity to extremes, especially when trying to explain cases of Near-Death Experiences wherein the subject has no detectable brain activity. They basically suggest that specificity allows for a handful of neurons, whose activity is too faint to be measurable, to hypothetically explain lifetimes of complex and coherent experiences. Resuscitation specialist Dr. Sam Parnia’s candid rebuttal of this suggestion seems to frame it best: 'When you die, there is no blood flow going into your brain. If it goes below a certain level, you can't have electrical activity. It takes a lot of imagination to think there's somehow a hidden area of your brain that comes into action when everything else isn't working.' But even if we grant that there is hidden neuronal activity somewhere, the materialist position immediately raises the question of why we are born with such large brains if only a handful of neurons were sufficient to confabulate unfathomable dreams.… Moreover, under ordinary conditions, it has been scientifically demonstrated that we generate measurable neocortical activity even when we dream of the mere clenching of a hand! It is, thus, incoherent to postulate that undetectable neural firings – the extreme of specificity – are sufficient to explain complex experiences.

Fron here, he moves on to the filter/receiver theory, which is actually a steppingstone to a less familiar model that he develops later. Here's how he introduces the filter idea:

If consciousness is primary and irreducible, it cannot be the case that the brain generates it. How can we then explain the empirical observation that, ordinarily, mind states correlate well to brain states? The hypothesis I submit is that the function of the brain is to localize consciousness, pinning it to the space-time reference point implied by the physical body. In doing so, the brain modulates conscious perception in accordance with the perspective of the body. When not subject to this localization and modulation mechanism, mind is unbound: it entails consciousness of all there is across space, time, and perhaps beyond. Therefore, by localizing mind, the brain also 'filters out' of consciousness anything that is not correlated with the body's perspective.

According to this 'filter hypothesis' of mind-brain interaction, no subjective experience is ever generated by the brain, but merely selected by it according to the perspective of the body in space-time… This selection process is akin to a 'filtering out' of conscious experience: like a radio receiver selecting, from among the variety of stations present concurrently in the broadcast signal, that which one wants to listen to, all other stations being filtered out and never reaching the consciousness of the listener. The brain activation patterns that ordinarily correlate with conscious experience reflect the filtering process at work: they are analogous to the circuit oscillations in the radio's tuner, which correlate tightly to the sounds the radio emits.

As I said, his actual view is monistic idealism, not dualism, so eventually he moves away from the filter analogy to a different metaphor: the mind as a whirlpool in the midst of a broader stream of consciousness, which Aldous Huxley called Mind at Large.

My hypothesis is that mind is a broad and continuous medium unlimited in either space or time; a canvas where the entire play of existence unfolds, including space and time themselves. Your egoic mind – that limited awareness you identify yourself with – is, in this context, merely a segment of the broad, universal canvas of mind. Your impression that your mind is separate from all the rest is… the result of a 'filtering' process induced by a specific, localized topological figure of the canvas of mind.

Just as a whirlpool is part of a stream but distinguishable from it, so the egoic mind is part of the vast current of Mind at Large. What makes it seem separate from "external" reality? The ego's self-awareness. Kastrup explains:

The ability to turn conscious apprehension itself into an object of conscious apprehension is what fundamentally characterizes our ordinary state of consciousness. In fact, my claim is that this is what defines what psychology calls the 'ego': the ego is the part of our psyches that is recursively and self-referentially aware.…

There is a very intuitive way to visualize this process of recursive, self-referential awareness: two mirrors facing each other. Each mirror reflects the image of the other, including its own image reflected on the other.… Each reflection can be seen as a step in the recursion of awareness, wherein an image becomes in itself part of another image of a higher level, and that image part of another image at a yet higher level, and so forth. Each image is both awareness at its own level and an object of awareness at a higher level. I submit to you that egoic consciousness is analogous to these two mutually-facing mirrors: our ordinary awareness is recursively self-reflective.

Because of this, any content of mind that falls within the field of self-reflectiveness of the ego becomes hugely amplified.… Any experience that falls within the scope of the ego is recursively reflected on the mirrors of awareness until it creates an unfathomably intense mental imprint. I submit to you that most things you are ordinarily aware of, like the book or electronic reader in your hands right now, are amplified like that.…

Now, if this is so, what happens to the experiences flowing in the broader medium of mind that do not fall within the scope of the ego? They do not get amplified at all. Therefore, from the point-of-view of the ego, they become practically imperceptible! This, in my view, is how we've come to speak of and 'unconscious' segment of the psyche. There is no unconscious; there are only regions of the medium of mind whose experiences, for not falling within the field of egoic self- reflectiveness, become obfuscated by whatever does fall within the scope of the ego.

Here is another analogy to help you develop an intuition for this. When you look up at a clear sky, at noon, you only see blue. You can't see the stars that, at night, would be unmistakably there. Yet the stars are all still there and their light is still reaching your eyes, just like it would at night. You can't see them because they become obfuscated by the much stronger glare of the sun reflecting on the atmosphere.… My view is that the 'unconscious' experiences flowing along the broader stream of mind are all still there in consciousness, at all times, interspersed throughout the amplified contents of egoic awareness, just like the photons from distant stars at noon.

Still later, he develops yet another metaphor - mind as membrane. In this analogy, the vast field of Mind at Large is likened to a broad membrane. Within the membrane there are folds, bumps, and loops, which constitute individual things (all entities and events being subjective experiences). Kastrup:

There is nothing to reality but the medium of mind itself. There exists nothing but the membrane. When the membrane is at rest, there is no experience as such, but only the potential for experience. After all, the membrane can start vibrating. When the membrane does vibrate, then experience arises. But what is a vibration other than the medium that vibrates? There is nothing to a vibrating guitar string but the string itself. As such, experiences – the 'contents' of mind – are nothing but mind itself, manifesting a certain behavior in the form of vibration.… This membrane is not something outside mind; it is not 'stuff'; it is mind itself as witness. And the witness witnesses its own vibrations.

How did this all come about?

I like to imagine the cosmological history of mind in the following way: in the very beginning, the membrane of mind was at rest. It didn't move or vibrate. Its topography and topology was as simple as possible: an entirely flat membrane without any bumps, protrusions, or loops of any sort. As such, not only was there no reflectiveness, but also no experience, since experience consists in the vibrations of the membrane. Only an infinite abyss of experiential emptiness existed; the deep, dreamless sleep of nature. Yet, such unending emptiness was not nothing, for there was inherent in it the potential for something.

At some point, some part of the membrane moved, like in an involuntary spasm. Instantly, this movement was registered by the one subject of existence as a very faint experience. There is a significant sense in which an experience concretizes – brings into existence – its very subject. The membrane realized, at that moment, that there was something. It is not difficult to imagine that such a realization could lead to a kind of surprise and agitation that immediately translated into more expansive modern movements, more experiences. Shortly the membrane of mind was boiling with vibrations.…

But since there were still no loops in the medium of mind, there was no self-reflective awareness. Existence was still a confusing maelstrom of instinctive experiences in which the subject was completely immersed.…

At some point, the thrashing about of the membrane caused a small part of its surface to fold in on itself, closing a hollow loop. Suddenly, there was a hint of self-reflective awareness. And it was enough: the idea of 'I am' arose in the mind for the first time.

But what about the empirical evidence for a vast period of history beginning with the Big Bang, in which the universe was devoid of any conscious entities? Kastrup notes that, according to idealism, the universe is in mind, not the other way around. Mind was always there, and what we call the universe grew out of its vibrations and fluctuations. But why do we perceive an order to the universe - patterns predictable enough to be called laws of nature?

Why do the patterns and regularities of experience suggest, by extrapolation, a complex past that precedes self-reflective awareness? That history could be the very cosmological history imagined above: there was indeed a past in which mind still had no loops or folds. The abstracted partial image of this cosmological past, as reconstructed by the human ego according to the preferred symbols of a particular culture or time, takes the form of a Big Bang, or a collision of hyper-dimensional membranes in M theory, or the pulling apart of father Sky from mother Earth, or of many other creation myths. Indeed, any historical account of a remote cosmological past is, fundamentally, a self-referential symbol in mind for the history of mind itself.

This, to me, was one of the less persuasive parts of the book. As I look at it, the universe seems to have come into existence with the rules already laid out. It doesn't appear to have been making up the rules as it went along in a series of random, spasmodic fluctuations. In other words, I would see the Big Bang as somewhat akin to booting up a computer program - the program is already written, and the boot-up simply gets it started. Of course, this leaves open the question of who wrote the program and where it is stored ...

Another aspect of Kastrup's argument that I found a bit unsatisfactory was his attempt to link the membrane hypothesis to string theory. He notes that one variation of string theory describes reality as essentially a single membrane vibrating in ten dimensions, a viewpoint that is at least consistent with his own model. But string theory remains controversial, empirical support for supersymmetry is so far lacking, and some physicists believe the whole approach may be a dead end. Even Sheldon Cooper on The Big Bang Theory has given up on it!

Moreover, if we're going to use physics models to bolster philosophical models, we probably need to explain such conundrums as wave-particle duality and quantum entanglement, which Kastrup doesn't specifically address. To my way of thinking, the notion of the universe as (ultimately) pure information, with physical phenomena as expressions of algorithmic transformations, is more compelling. See the website The Bottom Layer for a detailed look at how wave-particle duality and other paradoxes melt away when viewed in informational terms.

Getting back to the book, Kastrup tackles the question of life after death, writing:

It is reasonable to assume that the mental process we call physical death 'makes the unconscious more conscious,' because it eliminates a source of obfuscation; namely, the egoic loop. After all, physical death is the partial image of the process of unraveling of the egoic loop. As such, it is reasonable to expect that it causes us to remember all that we already know but cannot recall. From the ego's perspective, this may seem like receiving all kinds of new answers. But it won't fundamentally add any original insight to mind. The sense of novelty here is merely the illusion of an ego going through dissolution. Once the ego is gone and all is remembered, the sense of novelty will disappear.…

The question, of course, is whether self-reflective awareness disappears completely upon physical death.… If the ego is the only loop in the human psychic structure, then physical death indeed eliminates all self-reflectiveness. But it is conceivable that the psychic structure entails an underlying, partial, not-so-tightly-closed loop underneath the egoic loop. I say this because many Near-Death Experiences seem to suggest that a degree of self-reflectiveness and personal identity survive death. In this case, the ego would be a tight loop perched on top of another partial loop. Assuming that physical death entails the dissolution of only the egoic loop on top, then our awareness would 'fall back' onto the underlying partial loop, preserving a degree of self-reflectiveness. The result would be more access to the 'unconscious' – due to less obfuscation – but we would still maintain a sense of separate identity. This, of course, is highly speculative.

In this connection, it's worth noting that some mediumistic communications claim that, upon dying, the unconscious mind takes the place of the conscious mind. That is, the material ordinarily screened from our conscious attention becomes readily available, resulting in a much wider range of awareness. It's also worth noting that in the channeled book The Unobstructed Universe, the communicator insists that all of reality consists of vibrations of consciousness, a view that has much in common with Kastrup's membrane model.

Why are anomalous experiences more prevalent in traditional societies, such as the Zuruaha, than in the developed world? Kastrup:

Unlike all traditional cultures, Western civilization has reached a degree of technological and social advancement that allows for unprecedented levels of physical health and comfort.… In contrast, members of traditional societies were often exposed to the weather, to malnutrition, to extreme physical exertion, and to chronic health conditions. I suggest that such level of exposure would have compromised brain function sufficiently to induce non-ordinary states of consciousness on a regular basis. To put it simply, traditional people would be regularly exposed to what they called 'the otherworld,' a part of reality otherwise filtered out by well-functioning brains. Their nonlocal, transcendent experiences wouldn't be merely personal and idiosyncratic, but validated at a collective level, since most members of the society would also experience them.… Their ontology wasn't based on superstition, but on shared empirical observation recorded, thereafter, according to allegorical images and narratives peculiar to each particular culture.

Finally, what does it all mean, and how much can we ultimately hope to understand?

Since the eye that sees cannot see itself directly, mind can never understand itself literally. A literal – that is, direct – apprehension of the nature of existence is fundamentally impossible, this being the perennial cosmic itch. The vibrations of mind – that is, experiences – can never directly reveal the underlying nature of the medium that vibrates, in the same way that one cannot see a guitar string merely by hearing the sounds of produces when plucked. Yet, the vibrations of mind do embody and reflect the intrinsic potentialities of their underlying medium, in the same way that valid inferences can be made about the length and composition of a guitar string purely from the sound it produces. The sound of a vibrating medium is a metaphor for the medium's essential, underlying nature.…

As such, consensus reality is nothing but a metaphor for the fundamental nature of mind. Nothing – no thing, event, process or phenomenon – is literally true, but an evocative vehicle.… The plethora of phenomenon we call nature and civilization holds no more reality than a theatrical play.…

A metaphorical world isn't a less real place; on the contrary! Is a world where only essential meanings are ultimately true. It is a world of pure significance and pure essence.… All phenomena are suggesting something about the nature of mind.… A job loss, a new romantic relationship, a sudden illness, a promotion, the death of a pet, a major personal success, a friend in need… What is the underlying meaning of it all in the context of our lives? What are all these events saying about our true selves? These are the questions that we must constantly confront in a metaphorical world.

Though I remain more comfortable with a quasi-Kantian model of a noumenal realm of pure information and a phenomenal realm of "rendered" images perceived subjectively, I have to say that Kastrup's book has made me think. He's a good writer and a provocative thinker, and I recommend both his book and his blog.

Many cultures have seen a close connection between mysticism and madness — and in fact, there are significant similarities between behaviors associated with some forms of mental illness and the behaviors associated with mediumship (trance mediumship in particular). There are also areas of overlap between the intellectual fixations of some mental patients and the accounts of near-death experiencers.

Critics see these parallels as evidence that paranormal states of consciousness can be explained as instances of a psychological or neurological problem. Basically they say, “You’d have to be crazy to believe this stuff.”

I don’t agree with that assessment. But I do think it’s interesting and instructive to examine these similarities, which some people with spiritual inclinations may find troubling.

Anyone who's had the opportunity to spend time with a person suffering from delirium, schizophrenia, or dementia may have noticed some or all of the following behaviors:

Incessant talk about God, visiting heaven, and meeting with deceased relatives, often expressed with intense emotion.

Belief in out-of-body experiences and heavenly communications, including direct contact with God.

Periods of communication with an unseen presence, in which the patient will talk, with eyes closed, to someone who “isn’t there.”

Grandiose projects intended to save the world – projects that are admirably altruistic but mostly impractical.

Stream-of-consciousness speech, incredibly loquacious and verbose; the rapid production of large blocks of words, at a rate that would challenge the skills of a stenographer.

The insistence that everything is connected and is all part of a larger plan; the connections cited are trivial, random, and arbitrary, but are interpreted as profoundly meaningful.

The claim that “time is running out” and that some amazing, transformational event is about to take place, for which the world must be prepared.

The assurance that all these revelations are startlingly clear and make perfect sense, even though they seem nonsensical to observers.

I have personally observed all of the above.

Now, if we look at parapsychological phenomena, we can easily see areas of overlap with the behaviors listed above. Mediums, by definition, spend time talking to someone who “isn’t there,” at least in a mundane sense. Trance mediums who practice automatic writing are known for their incredible output, producing thousands of words with little apparent effort and with minimal need for revision. It has often been noted that those on "the other side" have no shortage of altruistic plans and projects, but that these schemes are generally impractical. There is also no shortage of failed predictions by mediums, usually involving some momentous event of world-shaking import.

Near-death experiencers often report that while they were out of their body, they understood that everything that happens is interconnected in a vast, beautiful, and perfect design. Some also report having had access to all knowledge with astonishing clarity, yet they are rarely, if ever, able to convey this clarity after being revived.

Such parallels go a long way toward explaining why mainstream psychiatrists, who often encounter delirious, schizophrenic, or senile patients, are generally skeptical of phenomena like mediumship and NDEs. There are, however, crucial differences that shouldn't be glossed over. The best cases of mediumship involve verifiable details that the medium had no normal way of knowing, and in some cases involve actually re-creating the characteristic mannerisms, gestures, facial expressions, and verbal tics of a deceased person unknown to the medium. The best NDE cases include veridical observations of things that took place while the patient was deeply unconscious or even clinically dead.

Even though it would be a mistake to conflate mental breakdown and paranormal mindsets in a simplistic way, the obvious similarities still require an explanation. Why should madness and mysticism be so closely linked?

My best guess is that the "mental filter" hypothesis popularized by Aldous Huxley in such books as The Doors of Perception is at least partially correct. This hypothesis holds that consciousness exists outside of the brain, rather than being created by the brain; the brain serves as a filter that shuts out the greater part of consciousness, allowing us to focus on narrower, more specific objectives consistent with survival on earth.

If the brain is damaged or its chemistry is altered, the filter starts to break down and normally restricted input begins to trickle in. The result is a subjective sense of mind expansion, a conviction of direct contact with "the beyond," and an urgent desire to communicate ineffable ideas. Unfortunately, there is a severe downside: the person's ability to function in the everyday world is seriously compromised. (Remember that the need to function in ordinary reality is the reason for the filter mechanism in the first place.)

Moreover, whatever legitimate input may be coming to the person’s attention is mixed together with erroneous or irrelevant thoughts – what William James called “bosh" in connection with the mediumship of Mrs. Piper. (As Michael Tymn notes in Resurrecting Leonora Piper, James characterized a great deal of what Mrs. Piper had to say while in trance as bosh or nonsense, while acknowledging that a smaller portion of what she said was not explicable by any normal means. It was this smaller portion that fascinated him and other investigators.)

The filter hypothesis is very ably explained and defended in Chapter 2 of Bernardo Kastrup’s new book, rather combatively titled Why Materialism Is Baloney. Kastrup, who maintains a blog arguing for philosophical idealism, notes that the filter hypothesis implies two important predictions. The first is that:

The subjective experiences that are filtered out become the so-called 'unconscious' mind of the respective ego. Since each ego allows in only an infinitesimally small part of all potential experiences – given the unfathomable variety of conscious perspectives that exist in potentiality – the 'unconscious' minds of different egos will differ only minimally, the vast majority of the 'unconscious' being identical across egos. As such, the filter hypothesis, unlike materialism, predicts the existence of a 'collective unconscious,' a shared repository of potential experiences that far transcends mere genetic predispositions of a species.

He finds evidence supporting this prediction in the work of analyst Carl Jung and the whole field of transpersonal psychology.

The second prediction is that there should be "a broad pattern of empirical evidence associating non-local, transpersonal experiences with procedures that reduce brain activity."

In support of this prediction he cites fainting caused by asphyxiation, pilots who lose consciousness when blood leaves the brain, hyperventilation, psychedelic substances, inhibition of brain activity via electromagnetic fields, brain damage, automatic writing practiced by trance mediums, near-death experiences, immersion in an isolation tank, and various initiatory rituals in tribal cultures. (“It is very reasonable to assume that such ordeals – like long sessions in sweat lodges, exposure to the elements, extreme exertion, and even poisoning – physically compromised brain function.”)

All of these cases, Kastrup argues, have been associated with nonlocal, transpersonal states of consciousness, strongly indicating at least a correlation between reduced or impaired brain activity and experiences of "cosmic consciousness" (to use the phrase coined by R.M. Bucke).

Kastrup notes that materialists often cite many of these cases as evidence that transpersonal experiences, being precipitated by biological changes, must be purely illusory. He counters with this argument:

Well, such an assumption is, in my view, the product of shallow thinking at best and of prejudice at worst. Just why can't a true transpersonal experience be triggered by physical intervention in the brain, given the obvious fact that mind and brain are related in some way? What is in dispute is the nature of this relationship, not its existence. If the nature of the relationship is such that the brain modulates and localizes consciousness, without causing it, it is not only reasonable but also expectable that physical interference with the brain should change one's subjective state. Not only that, partial deactivation of certain brain processes through physical means – be them psychoactive drugs, magnetic fields, hyperventilation, asphyxiation, ordeals, sensory deprivation, etc. – should allow consciousness to partially de-localize and expand, which is perfectly consistent with the types of transpersonal experience listed above …

While particular reports of transpersonal experiences could possibly be explained away, the broad pattern that associates peak transpersonal experiences with reductions of brain activity clearly points to a robust and consistent phenomenon.

To change the analogy slightly, let’s look at the brain not as a filter but as a receiver. The two metaphors are closely related; each assumes that consciousness originates outside the brain, and that the brain must modulate the inflow of consciousness in some way. A radio receiver can be tuned to any number of frequencies. In effect, the tuner is designed to "filter out" unwanted frequencies and allow only the desired frequency to come through. As long as the radio is tuned to a clear signal, the information will come through with minimal distortion.

But suppose something goes wrong with the tuner. Suppose the radio starts randomly jumping from one frequency to another. It would, in one respect, be accessing more information – or at least a broader range of information – than before. Yet the resulting transmissions would be confused and chaotic, because the dial would keep slipping unpredictably from one station to another.

Or suppose the radio acquired the ability to tune in to more than one station at a time. Then two or more transmissions would come through together. If one signal was stronger than the others, it might come through clearly enough, with only faint "ghost" transmissions in the background. (The term “ghost” is an interesting one in this context.) But if all the signals were of approximately equal strength, the resulting noise would be almost impossible to interpret. Technically, more information would be coming through; but it would be indecipherable.

There's an episode of Buffy the Vampire Slayer titled “Earshot" in which Buffy develops clairaudience – she can hear other people's thoughts. At first she finds this new found talent helpful. But as the episode progresses, her clairaudience increases, until she hears a babble of voices in her head at all times, a condition that incapacitates her and threatens to drive her insane. Though I doubt it was intentional, this storyline is a good metaphor for the benefits and hazards of impairing the brain’s “filter” mechanism.

We can probably see now why mental illness and paranormal states of mind have significant areas of overlap. In both cases, the brain's function as a filter (or tuner) has been compromised, letting in a stream of information that would ordinarily be kept out. Within limits, opening up the filter can be beneficial; outside those limits, it can do more harm than good.

In short, the filter hypothesis seems to provide a pretty good explanation for the way in which mental breakdown dovetails with trance mediumship and NDEs. The alternative explanation, proffered by materialists, would be that the communications provided by mediums and the narratives recounted by NDErs are themselves instances of mental illness or temporary mental breakdown. But this viewpoint doesn’t account for the veridical aspects of these cases, or for the fact that, typically, mediums and NDErs are able to function quite normally in their everyday lives.

All that having been said, there’s one more thing to consider. Many cultures, both ancient and modern, have taboos against delving too deeply into the paranormal. It’s possible that such taboos serve a legitimate purpose, and should be violated only with caution. If the brain’s filtering activity is indeed essential to allowing us to navigate the physical world, then any impairment of the filter may reduce our survival prospects. In fact, natural selection seems to dictate that really strong psi talents would be progressively weeded out of the population, since whatever advantages psi might offer would be more than offset by the risk of being overwhelmed and disoriented by excessive mental input. (On the other hand, more moderate psi talents would not necessarily face extinction, and higher level talents could be cultivated with practice or might appear spontaneously in rare cases, either at birth or as a result of some alteration in brain function. Cultures that placed a high value on shamanic talents would look after such individuals and see to it that their everyday needs were met.)

For millennia, mystical adepts have warned casual enthusiasts not to get caught up in things beyond their ken. It’s worth keeping these injunctions in mind. The mind-brain relationship can be a fragile thing; we toy with it at our peril.